[App_rpt-users] Jim and Ramesh (chan_voter and RPi)

Corey Dean n3fe at repeater.net
Thu Dec 27 18:22:42 EST 2012


My thought on this would be if it couldn't handle the DSP and had to rely on simple USB then it wouldn't be able to work as a voter because it wouldn't be able to read the RSSI of the discriminator audio.   I may be way off on my thought, but I know it needs DSP for the discriminator audio.

Corey  N3FE

-----Original Message-----
From: app_rpt-users-bounces at ohnosec.org [mailto:app_rpt-users-bounces at ohnosec.org] On Behalf Of Shane Morris
Sent: Thursday, December 27, 2012 2:56 PM
To: app_rpt mailing list
Subject: [App_rpt-users] Jim and Ramesh (chan_voter and RPi)

Hi all,

I was thinking, even though the RaspberryPi can't handle the audio stream from a URI due to the limitations of the USB bus, what is the ethernet performance like? I imagine it wouldn't be terribly good, due to the fact the ethernet swings off the USB, but hear me out...

chan_voter is a module that communicates via ethernet, am I correct?
It uses an RTCM connected over an ethernet bus to communicate the voice data around, and I can imagine, at a low codec rate like GSM or even Speex, throughput wouldn't be as excessive as raw sound data coming from a fob.

So my proposal is, before Jim and Ramesh throw out the baby with the bathwater, and consign the RPi effort to the dust, why not take the work, which I believe involves getting Zaptel/ DAHDI to work with the RPi, and apply it to a purely chan_voter system? Yes, I know the chan_voter is dependant upon app_rpt, and in the future, someone, somewhere, is going to try to hook up a sound fob, and miserably complain it doesn't work, but we get the same questions about Asterisk
1.8 over and over too, right?

The advantages here are manyfold - again, low power consumption comes into the game, everyone knows I personally need as low a power consumption as I can get. The fact the RTCM data (ie, VoIP over
ethernet) is much more suited to the infrastructure on the RPi is a good thing here too. The fact that normal Asterisk just runs, and runs well, on RPi is another motivating factor - my friend Andrew is running his house PABX on an RPi running Asterisk 1.8 I believe, there is an image for this. And yes, simply the cool factor - who else can say they run their voting repeater system off something the size of a credit card, with all the proprietary, messy, rack mounted stuff out there?

If Jim and Ramesh are unwilling, or unable, to help, due to the fact that the RPi is a bit of a letdown (I heard about the USB performance issues - ouch!), I would like to take their work, and apply it to a platform I think may have a bit better USB performance - its based on a Cortex-A8 (ARMv7) - the Cubieboard. For all you I/O junkies out there, what can YOU do with 96 I/Os? For $49, gets you something good, look it up, www.cubieboard.org - I got one for Christmas, and I thought it would be good for this. Its a Chinese Allwinnner A10 device.

Since I have gone beyond just simple URI systems since Jim introduced me to the RTCM, I would like to get this to work. I recognised the RTCM did something I was talking to Andrew about on the way home from Expedition in October of this year - "Wouldn't it be nice, Andrew, if we could have a voting system that allows us the flexibility to run an Expeditions communications in such a way that make it simply easy for us, and easy for the users?" Before, we've had users change channels in different places, this inevitably leads to confusion. With a chan_voter system, we can run the same UHF CB channel across the arena, and access it anywhere.

Andrew had said to me "Shane, do you know how much such a system would cost...?" Yes, Andrew, I had the Simoco, and I bought the RTCM for
$250 second hand ^.^ Sorry for being a smart-alec, I know you meant how much would a PROPRIETARY system cost us?

Anyway, I hope I have Jim and Rameshes blessing on this one - they did some great work, and I know it must've been a letdown to find out the hardware simply wasn't up to the task. Believe me, this isn't the first story I've heard about the lacklustre I/O performance of the RPi, and it won't be the last. But by using their work on a much stronger (I hope!) platform that it still ARM Linux based, I hope to circumvent at least one problem with the RPi. And its only $11 more before shipping!

Looks like I'm going to be reading the Allwinnner A10 device spec sheet now, huh? =)

Thanks for putting up with my ramble everyone.

Shane.
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